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An atmospheric mechanism for ENSO amplitude changes under an abrupt quadrupling of CO 2 concentration in CMIP5 models
Author(s) -
Rashid Harun A.,
Hirst Anthony C.,
Marsland Simon J.
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl066768
Subject(s) - forcing (mathematics) , amplitude , coupled model intercomparison project , climatology , radiative forcing , atmospheric sciences , sea surface temperature , environmental science , climate model , wind stress , el niño southern oscillation , coupling (piping) , oscillation (cell signaling) , climate change , physics , geology , materials science , oceanography , chemistry , biochemistry , quantum mechanics , metallurgy
We investigate the impact of a quadrupled CO 2 concentration on the simulated El Niño–Southern Oscillation (ENSO) amplitudes in 19 Coupled Model Intercomparison Project phase 5 (CMIP5) climate models. The amplitude of ENSO‐related sea surface temperature (SST) variability decreases in 11 of these models, and increases in the rest, in response to the enhanced radiative forcing. These opposing amplitude changes are predominantly explained by opposite changes in the time‐lagged SST response to a given central Pacific zonal wind stress (ZWS) forcing, with the net heat flux forcing and the SST‐ZWS feedback playing smaller roles. We find a robust relationship between the changes in the ZWS forcing efficiency and those in the ZWS‐deep convection coupling in the central‐western Pacific, indicating an important role for this coupling in ENSO amplitude changes. Indeed, the projected change in this coupling is indicative of the projected change in ENSO‐related SST variability.